To be quite honest, i heard no difference in the tones. You either aren't boosting right, or the way you recorded these tracks is making it lose the elements which make boosting so prominent.
When im playing my Bugera 6262, which is probably the closest thing to a 6505 besides a 5150, when i turn off my tubescreamer, there is a NOTICEABLE loss in gain and clarity and increase in flubby bass. The difference is amazingly clear with my setup.
I know everybodies ears and equipment is different, but i still couldn't help but feel your tone should sound more different with the pedal activated.
EDIT: I actually did notice on Resolve, track b is significantly louder and has more presence. That big change in volume leads me to believe it wasn't mixed the same in your program though, because on the rest of the tracks there is no volume change.
Check out my band. Add us!